chore(lint): apply ruff --fix (4443 auto-fixes)

Auto-fixed categories:
- F401: unused imports removed
- I001: import blocks sorted
- W293: trailing whitespace stripped
- UP035: deprecated typing imports replaced
- SIM: simplify suggestions applied
- ARG: unused args prefixed with underscore
- T201: print statements removed
- F841: unused variables removed
- RUF059: unpacked variables prefixed

Remaining ~1500 unfixable errors (C901, B904, N806, E402) require manual work.

Backend smoke tests: 13/13 passed.

backend/tests/test_auth.py

@@ -13,16 +13,17 @@ from pathlib import Path
 sys.path.append(str(Path(__file__).parent.parent / "src"))
 
 import pytest
+from cryptography.fernet import Fernet
 from sqlalchemy import create_engine
 from sqlalchemy.orm import sessionmaker
-from cryptography.fernet import Fernet
-from src.core.database import Base
-from src.models.auth import User, Role, Permission, ADGroupMapping
-from src.services.auth_service import AuthService
+
 from src.core.auth.repository import AuthRepository
-from src.core.auth.security import verify_password, get_password_hash
+from src.core.auth.security import get_password_hash, verify_password
+from src.core.database import Base
+from src.models.auth import ADGroupMapping, Permission, Role, User
 from src.scripts.create_admin import create_admin
 from src.scripts.init_auth_db import ensure_encryption_key
+from src.services.auth_service import AuthService
 
 # Create in-memory SQLite database for testing
 SQLALCHEMY_DATABASE_URL = "sqlite:///:memory:"